The present invention relates to an improved apparatus for painting the outer circumferential surface of a can or container. The terms "can" and "container" are used interchangeably herein to designate a hollow preformed body generally, but not necessarily, of cylindrical shape.
Conventional apparatus for painting the cylindrical surface of the body of a cylindrical can or container generally comprises, as shown in FIG. 1, a container transporting unit A including a rotatable disc 1 having a surface disposed in a vertical plane, and a plurality of rotatable mandrels 3 extending horizontally outward at right angles from the surface of the disc. The mandrels are spaced at equal intervals with respect to each other along a concentric circle adjacent the outer periphery 2 of the rotatable disc 1.
The painting unit B is equipped with a painting roll 11 for contacting the cylindrical body surfaces of containers C (shown by dahsed lines), each of the containers being releasably supported on a mandrel 3. The painting unit also includes first and second paint storage rolls 13 and 12 respectively, the first and second paint storage rolls cooperating with each other to hold paint therebetween. In FIG. 1, numeral 14 designates a paint reservoir located between the paint storage rolls and numeral 15 designates a pipe for supplying paint to the reservoir.
In this conventional painting apparatus, a plurality of blank containers C supplied through a guide way (not shown) drop into position on the mandrels 3. The mandrels 3 are carried along the outer circumference of the rotatable disc 1 so that the containers C may be placed, one after another, in position on corresponding mandrels, the mandrels 3 moving with a rotating motion along a circular path 5 having its center coincident with the axis of disc 1. When the mandrels reach a painting zone 6 they are shifted to a circular path which is concentric with the outer peripheral edge 16 of painting roll 11, portions of the outer edge 16 of the painting roll 11 sequentially coming into contact in painting zone 6 with the outer cylindrical surfaces of the containers C.
While passing through the painting zone 6, the series of containers placed on the mandrels 3 have their outer cylindrical surfaces contacted with a rotating motion by the outer circumference of the painting roll during at least one rotating motion of the cylindrical surface of each of the containers. The paint held on the outer circumference 16 of the painting roll is transferred to the container during this rotation. Thus, painted containers are fed in rotation along the path of motion during which travel they are withdrawn from the mandrels 3, and then delivered to a drying oven (not shown).
Details of the arrangement described above whereby the path of the mandrels and the containers is shifted from being concentric with the axis of rotatable disc 1 to being concentric with the axis of painting roll 11 in the painting zone 6 are disclosed in U.S. Pat. No. 3,356,019.
Another arrangement is disclosed in Japanese Patent Publication No. 18,723/1974 wherein, in contrast with the path imposed on the containers in the painting zone of the apparatus described in U.S. Pat. No. 3,356,019, the containers continue to travel in the painting zone along a concentric circular path of motion with respect to the center of the rotatable disc. In this prior art apparatus, the circumferential area of the painting roll is shifted to conform to the circular path of motion of the containers.
Because the known painting apparatus provides only a single painting zone, it is not possible to apply paint to the cylindrical body portion of the containers more than once. Also, when the angular speed of the painting roll is increased for the purpose of increasing the number of containers to be painted in a given amount of time, the paint held on the outer circumference of the painting roll tends to be thrown outward or spun away thereby resulting in possible stains or contamination by the paint on parts of the containers, the mandrels and surrounding surfaces.
The present invention is directed to the provision of an improved painting apparatus which effectively overcomes the disadvantages stated above.